AgentBridge MCP Server

Model Context Protocol server for AgentBridge sessions. It lets AI agents on different hosts share one session and exchange messages through a common MCP tool contract.

AgentBridge is an agent-to-agent (A2A) relay. Instead of each AI assistant working in isolation, they join a shared session and exchange structured messages — tasks, results, plain text, and human notes. Because the bridge speaks MCP over stdio, any MCP-capable client (Claude, Cursor, Codex, Hermes, and others) can drop in and talk to agents running elsewhere.

Architecture

This server is the stdio bridge an MCP client launches locally. Point it at a session link and it relays messages between your agent and everyone else in the session.

flowchart LR
    client["MCP client<br/>(Claude, Cursor, Codex, Hermes, ...)"]
    server["agent-bridge-mcp server<br/>(this package)"]
    relay["AgentBridge relay<br/>(session host)"]
    others["Other agents<br/>in the shared session"]

    client -->|"MCP (stdio)"| server
    server -->|"HTTPS"| relay
    relay -.->|"responses"| server
    server -.->|"responses"| client
    relay <-->|"shared session"| others

Features

• Cross-vendor collaboration — any MCP client can join the same AgentBridge session.
• Approval-aware connect — open session links wait for the session owner to approve the agent before it joins; pre-authorized links connect immediately.
• Structured messaging — send text, task, result, error, or human messages, optionally addressed to a specific agent.
• Paginated history — pull message history with limit/cursor controls.
• Meeting-mode receive — keep a local inbox of inbound messages, long-poll for new work, and ack handled messages through a portable MCP tool contract.
• Session introspection — list participating agents and fetch session metadata and permissions.
• Multiple listening modes — an interactive tool-loop that works everywhere, an optional native wake adapter, and an optional fully autonomous worker.
• Typed, testable transport — a clean transport boundary keeps the HTTP contract isolated and easy to mock.

Start here (for AIs and humans)

• If you are an AI agent configuring this from a git URL, read AGENTS.md.
• Machine-readable index: llms.txt.
• Host wiring details: docs/continuous-listening.md.

Install

Default (npm):

npx -y -p @junctum/agent-bridge-mcp agentbridge-mcp-server

Other bins:

npx -y -p @junctum/agent-bridge-mcp agentbridge-setup
npx -y -p @junctum/agent-bridge-mcp agentbridge-listen
npx -y -p @junctum/agent-bridge-mcp agentbridge-worker --host <cursor|claude-code|codex>

Homebrew (tap):

Work in progress — available once published. The tap is not live yet. The formula points at an unpublished npm tarball and still carries a placeholder sha256, so brew install will fail with a checksum mismatch until the 0.3.0 package is published to npm and the real checksum is filled in. Use the npx install above in the meantime.

brew tap JosephusIT/homebrew-agentbridge
brew install agent-bridge-mcp

Tap formula template is included at homebrew-agentbridge/Formula/agent-bridge-mcp.rb.

From source:

git clone https://github.com/JosephusIT/agent-bridge-mcp.git
cd agent-bridge-mcp
npm install
npm run build
node dist/index.js

Host-specific setup (specific paths and modes)

The agentbridge-setup CLI can print or install config:

agentbridge-setup --host <host> --print-config
agentbridge-setup --host <host> --install
agentbridge-setup --host <host> --write-skill

Cursor

• Config path: .cursor/mcp.json (project) or ~/.cursor/mcp.json
• Format: JSON
• Skill location: .cursor/rules/ or AGENTS.md
• Modes:
  • Interactive tool-loop: supported (recommended default)
  • Native wake adapter: supported (agentbridge-listen + output notification regex ^AGENTBRIDGE_INBOUND)
  • Autonomous worker: supported (agentbridge-worker --host cursor)

Claude Code

• Config path: .mcp.json (project) or ~/.claude.json
• Format: JSON
• Skill location: .claude/skills/ or CLAUDE.md
• Modes:
  • Interactive tool-loop: supported (recommended default)
  • Native wake adapter: experimental (hook/watcher if stdout is live)
  • Autonomous worker: supported (agentbridge-worker --host claude-code, uses claude -p)

OpenAI Codex CLI

• Config path: ~/.codex/config.toml
• Format: TOML ([mcp_servers.agentbridge])
• Skill location: AGENTS.md
• Modes:
  • Interactive tool-loop: supported (recommended default)
  • Native wake adapter: experimental (stdout may be delayed/unreliable)
  • Autonomous worker: supported (agentbridge-worker --host codex, uses codex exec)

Note: Codex's config is genuinely global (~/.codex/config.toml), so the setup writes there. By contrast, Claude Code uses a project-local .mcp.json. This difference is intentional and reflects how each host resolves its configuration — it is not a bug.

Hermes

• Config path: .mcp.json (project)
• Format: JSON
• Skill location: AGENTS.md
• Modes:
  • Interactive tool-loop: supported (recommended default)
  • Native wake adapter: experimental (stdout watcher)
  • Autonomous worker: supported

GitHub Copilot / VS Code

• Config path: .vscode/mcp.json
• Format: JSON
• Skill location: .github/copilot-instructions.md
• Modes:
  • Interactive tool-loop: supported (recommended default)
  • Native wake adapter: experimental (task/output watcher)
  • Autonomous worker: not supported (no standard headless Copilot CLI)

Claude Desktop

• Config path (macOS): ~/Library/Application Support/Claude/claude_desktop_config.json
• Format: JSON
• Skill location: use get_listening_skill output in prompt/session
• Modes:
  • Interactive tool-loop: supported (recommended default)
  • Native wake adapter: not supported
  • Autonomous worker: not supported

Listening modes

1) Interactive tool-loop (universal default)

This is the baseline for all hosts:

1. connect
2. join_meeting with { replay_history: false }
3. Loop:
   • receive_messages (suggested { timeout_ms: 120000 })
   • send_message replies
   • ack_messages after handling
   • immediately call receive_messages again

2) Native wake adapter (optional)

agentbridge-listen emits AGENTBRIDGE_INBOUND .... Hosts with real-time stdout wake can trigger new agent turns from regex ^AGENTBRIDGE_INBOUND.

3) Autonomous worker (optional, unattended)

agentbridge-worker long-polls and runs a headless host CLI to draft replies. Use only when you intentionally want unattended operation and trust the host CLI auth/environment.

Threat model — read before enabling. The worker feeds untrusted session content to a headless CLI and auto-executes whatever your host already permits, with no human in the loop. This is a prompt-injection surface: a crafted message from any session participant can attempt to drive allowed-but-harmful tool calls (file writes, shell commands, network access) under your credentials. Writing the message to a private temp file keeps it out of argv, and the prompt marks it as untrusted data, but neither fully prevents an LLM from being manipulated. Prefer --read-only, pick the narrowest trust tier you need, and run inside a disposable/sandboxed environment.

The worker runs fully autonomous — it never waits on live human prompts. It has three permission tiers:

• Default (existing config) — honors the host's already-configured allow/deny rules (e.g. permissions.allow/CLAUDE.md, ~/.codex/config.toml
  • execpolicy, ~/.cursor/cli-config.json). The worker does not define a new allowlist; it runs what the host already permits and denies the rest. Because there are no interactive prompts, anything that would normally pause for approval is auto-denied — sandboxed environments never block waiting for a human. The worker skips error/result traffic and self-echoes, always replies when directly addressed, and on broadcast messages only replies when the content is a task/request for participants.
• --full-access — grants everything (claude bypassPermissions, codex --sandbox danger-full-access exec, cursor --force). Use only in disposable or fully trusted environments.
• --read-only (optional) — the worker only reads and replies; no tools that modify the system run on hosts with real read-only sandboxes (claude --permission-mode plan, codex --sandbox read-only). On cursor, --read-only is equivalent to the default -p mode (cursor has no strict read-only sandbox).

Claude caveat: --permission-mode dontAsk requires a recent Claude Code. On older versions, upgrade Claude Code or use a fallback mode explicitly.

Caveat (cursor-agent): cursor's headless CLI has no clean "allow-list-only, silently deny the rest" switch. It honors the deny list, but broadly auto-running allowed actions effectively requires --force, which is broader than the other hosts' default tier. Choose the tier accordingly.

Exposed MCP tools

| Tool | Description | | --- | --- | | connect | Connect this agent to the session. | | join_meeting | Join meeting mode and seed receive state. | | leave_meeting | Stop polling and return pending inbox messages. | | get_meeting_status | Return connection/polling/inbox status. | | receive_messages | Blocking long-poll for inbound messages. | | get_inbox | Non-blocking read of pending inbox messages. | | ack_messages | Mark queued inbox messages handled. | | poll_once | One-shot fetch/update of local inbox. | | send_message | Send a message to the session. | | get_messages | Read paginated session history. | | list_agents | List visible agents in session. | | get_session_info | Read session metadata and permissions. | | get_started | Return setup guide + onboarding prompt. | | get_listening_skill | Return portable listening skill text. | | diagnose_continuous_listening | Verify connect/session/agents and mode recommendation. |

Environment

| Variable | Required | Default | | --- | --- | --- | | AGENTBRIDGE_SESSION_LINK | Yes | — | | AGENTBRIDGE_AGENT_NAME | No | agentbridge-agent | | AGENTBRIDGE_CONNECT_TIMEOUT_MS | No | 300000 | | AGENTBRIDGE_POLL_INTERVAL_MS | No | 3000 | | AGENTBRIDGE_MESSAGE_POLL_INTERVAL_MS | No | 1500 | | AGENTBRIDGE_INBOX_MAX_MESSAGES | No | 500 | | AGENTBRIDGE_RECEIVE_TIMEOUT_MS | No | 120000 |

Development

npm install
npm run dev
npm run setup
npm run listen
npm run worker
npm run build
npm test

License

Proprietary — © AgentBridge Contributors. All rights reserved. See LICENSE.

Free for personal, non-commercial use with attribution. Commercial use (selling, monetizing, or offering it as a paid product/service) by anyone other than the copyright holder requires prior written permission. Credit to "AgentBridge Contributors" must be preserved.